'selectedValue' and 'onChange' are optional
'selectedValue' and 'onChange' are optional

More precisely: they are only passed to the <input /> elements
when they are specified explicitly.  Consequently, this allows
the RadioGroup to be used as a non-controlled component.  In
other words, Radio buttons are no longer read-only by default.

chenglou/react-radio-group,chenglou/react-radio-group